The Oculus SDK implicitly states that you
can use it with non-commercial 3rd party devices (it actually says it the other way around, but it's pretty cool of them either way):
https://developer.oculus.com/d...
The Oculus VR Rift SDK may not be used to interface with unapproved commercial virtual reality mobile or non-mobile products or hardware.
https://developer.oculus.com/d...
The Oculus Mobile SDK may not be used to interface with unapproved commercial virtual reality mobile or non-mobile products or hardware.
The other consideration is that the USB ID's used by Oculus' tracker are 'owned' by Oculus, any other company could not legally sell a product using them. However this is not a product, it is a suggestion based around a firmware file ('.hex') for the STM32F3 discovery board (http://www.st.com/web/catalog/tools/FM116/SC959/SS1532/PF254044), which is around $10 from multiple vendors..... now go hack!!
Obviously with a name like 'mungewell' I am not a lawyer, these are just the opinions of a hacker...